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University of Jordan Faculty of Agriculture Department of horticulture and crop science Protected Agriculture(0641322) Dr. AZMI ABU-RAYYAN. Introduction
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University of Jordan Faculty of Agriculture Department of horticulture and crop science Protected Agriculture(0641322) Dr. AZMI ABU-RAYYAN
Introduction • It is the intensive cultivation of vegetables crops under protective structures (GH, PH, low tunnels, hot beds ----- mulch) having many objectives: • 1- High quality and quantity. • 2- Off season production. • 3- Elongation of growing season (early and or delay). • 4- Higher profit as consequence. • This is possible, since we are able to manage: • Providing the protective plants with proper Env. Conditions (Temp. ↓or↑, R.H.↑or↓, light intensity ↓or↑ and CO2 ↓or↑). • Providing the plants with proper Nutritional requirements. • Providing the plants with well prepared soil, free from diseases, using resistant CSV's or free from diseases, or using sterilized growing media or fertilizer solution in soil less cultivation.
This sector is differing from open field system in techniques to be applied but with similar basics. • Points of differences are: • Production cost is much more → more Efficient use of land (vertical extend and increase plant population as much as possible.) → increase production → increase profit. But in the same time much more risks (diseases, pollination problem fertilizers shortage as a result of monoculture and intensive cultivation system, heating and cooling problem, ventilation, light intensity. • These risks, make the sector under continuous check using developed equipment that enable resolving any problems in relatively short time as the presence of irrigation system, fertilization one, heating, cooling ventilation as well as presence of professionals to control pests problem effectively. • All these are costing factors which need a real capital to be employed and experienced farmers which are able to face and resolve any sudden problems in the field or in the market.
4-In any time and as a result of high cost of production → farmers are ready to use any further idea to increase their profits or to save their crops from any sudden problem. This leads in many cases to unwise utilization of the factors (to increase production or to overcome the problem) leading to possibility of very high pollution than in case of open field cultivation. 5-To certain extent, you can control time of production according to the market demand. (Degree day). 6-Keeping continuous quality of the product for long period of season. This standard quality is deeply related to the level of production factors effectuated and type of protective structures and their efficiency in controlling the variations in environmental condition including covering materials.
So, all these points lead to off season production and increase the production as a result of intensive cultivation and elongating the growing cycle → higher profits (if marketing is programmed in well manner, otherwise the opposite will occur. Also protective structures are highly need for isolation and breading programs, production of valuable plants as flowers and indoor plants (that characterized by high profits) and as nurseries and for hardening purposes. More than 400,000ha is the area utilized for production under protective conditions in the Mediterranean region 2.5% of that is covered with glass, 17.5% as plastic houses, 50% is covered with mulch and 23% is covered with low tunnels. USA, Japan, Holland, France, Spain, Italy, Belgium, Germany and Grand Britain are first countries in world in this sector. Low tunnels, in addition to their function as nurseries and for hardening purposes. Also can be utilized for watermelon and muskmelon and strawberry cultivation. To anticipate melon production by being covered at early growth stages. They are proper for farmers of low budget and can realize a good profit if managed well.
Tomato, Strawberry, Pepper, Cucumber, Squash (Hybrid), Eggplant, Lettuce, Melon and Beans are the main vegetables to be cultivated under protection showing two production periods: early: April-June and late in Autumn except for lettuce that could be produced mainly from January-March (Esbjerg for summer). This not valid for J.V.: early (autumn) from November to February and late (spring) from March to May or June. Also the activity of nurseries (for vegetable seedling production, flowers, indoor plants) is much related to the planting time of plants in permanent field (open or protective). They are well prepared, control of R.H, heating, parasite----- etc.). In Jordan: protection of vegetables had started in J.V. at 1968 with 2 Plastic Houses in Dir- Alla station. One was planted with various cucumber cvs while the other with tomato hybrid cvs .
J.V. is a very big natural G.H in which you can produce summer vegetables in winter time without heating but under protective structures. But there are some limits that decrease the production, the quality or some times eliminate the production totally as: • - low temp. during clean sky nights → heat inversion. • low temp. during the 40days (22/12-2/2). • for improving the quantity and quality of the protected vegetables there should be the use of protective structures and the covering sheets (pH, GH and tunnels). By protection, tomato production had increased from 1.5 ton/donum in open → 10 ton/donum of P.H. and 1ton/donum in open → 8ton/donumP.H. for cucumber. • In 1980’s, protection techniques had spreaded to hilly land for (1) having early production in hilly are and (2) extending it into autumn producing in months of off production in J.V.
(July, August, September and October). (3) cost of pest control in J.V. (4) severe depletion of input resources.
The % of protective is low because of: • No need to protect all vegetables as roots, tubers. • Protection is highly costed. • Low income of major part of farmers. • also increase production → decrease profit since exporting to the outer markets is limited → diversification
Means of Protection • From non favorable condition • The non favorable conditions which affect negatively the quantity and quality or cause death of plants are: frost, minimum temp. or below, max: temp. or above, winds (cold, hot, sandy----), high, low light intensity, hail and others. • The means of protection were developed from simple to highly sophisticated and complete automatic GH’s. they are: • Selection of protective place and using the proper method of cultivation, (in between mountains or in southern side of the mountain or south-Eastside to gain earlier warming condition and anticipate the spring planting time. Also making bed with slope towards south. Planting your plants in west or north side of the furrow to be directly exposed to sun shine.
2-Protecting the planted area by fences (hedges) (as like 2-3 lines of corn, sunflower, cactus, roses) against animals, winds, thieves and sand. These fences can be sufficient especially for vegetables of bus by growth (not vertical) where no need to do wind breaks to avoid loss of certain part of your land by shading and very low cost of wind breaks construction. 3-Wind breaks: if there is a sever wind, and sandy conditions they are build to filtrate the prevail wind (perpendicularly) as like 1)- living plants (pines, casuarinas ----) in a one or 2 lines (alternative) according to wind severity (1.5-2m between plants × 2-3m between lines) leaving about 8-10m in south or east sixes without planting since wind break will induce shading later on. *Characters of plants to be used are: 1) Ever green 2) of high growth rate into the upright and laterally. 3) Hard wood to tolerate wind force 4) not to be a source of pests infections.
2) Sterns of semi woody plants to be fixed in soil or built as not as those corn, sugar can ----- leaving space between each strip and other, so as to filtrate the strong wind and absorbing it’s force 3) nets of plastic strips to decrease the wind velocity and not to block (since blocking creates forces behind the nets which can destroy both the break and crop). So they are filtrating about 50% of wind speed. Can be established with more than one line. Should be treated against negative effect of U.V. light so as to elongate their life up to 5 years. They have advantages of non competing your crop on water or nutrient elements and not to be as a host for pests. 4) Caps of plants: that protect from winds and sands and can anticipate the production by rising temp.
little bit more than non covered and so non severe frost is overcome. They are of inverted V over cucumber against wind, hot tent over melons during low temp. where ventilation is done by cutting certain part 3-5cm from the side opposite to prevailed strong wind and this cut is very high as plant grown and very high in size up to be removed as the plant becomes in touch with the inner side of the cover. Ventilation is important to get rid of RH% and hardening well established plant. Disadvantages: exposing to decrease temp. after increase temp. can harmful the plants since during high temp we will have soft, sensitive plants to cool conditions. 5- Spraying the plant by mist water when temp. is around freezing level to release energy (80 cal/gm of water) when frozen which can to certain extent protect plants especially if the sprayed water is heated. It is practically applied for farm of citrus..
6- Spraying the plants with foam (as Agri-foam (commercial name) of Gelatin protein and stabilizer material for the foam and spreading one at the night of expected frost. It has been proved to be efficient in protected melon by very high temp. 12c > non treated since treated have been isolated from atmosphere and energy released from soil will be conserved for plants. Done by having source pf compress air to pass through a sponge surface that covered with foam material → small air foams which will be covered with membrane of the foam material which will an in volume up to cover plant. 7- Smoking over plant during frost nights → Radiahrns Air mixing to mix the upper warm with lower cold air in calm conditions. 8- The use beds are cold or hot for production of seedling early in season when low temp. is dominating. These beds should established near farm serves as water and over a well drained soil and protected by wall of farm building or behind wind break and well exposed to sunshine. It is firmed from bed (soil or sand or mix), over which frames of wood or cement are established with 45-60cm for northern side × 22.5-45 for southern side as height × cover frame (cloth, glass or plastic of 180cm × 90cm exactly as dimension of base bed.
Methods of Heating in hot beds: • Non fermented manures × straw with 2 : 1 ratio that prepared 10-14 days before being used as covered a pile that moistened and mix each 3 days to have uniform decomposition. Then spreading at the bed base to 30-90cm height according to the time needed to have heating (where 30-45cm gives heating up to 3-4 weeks while 60-90cm give heat up to 3 months). The base of bed should be well drained to draw down the excess moisture which if remain will block the fermentation and heat evolve. Normally, it is distributed: 12.5cm manure then pressed uniformly then another one up to final height distributing the top a layer of soil of 5-15cm for having uniform heat distribution and avoiding hot spots that may burn plants or seeds. Warm moistened manure shows > rate of decomposition than the cold moistened one.
Hot air: released heat of wood, methane or fuel burning is carried and pump ed as hot air to end of pipes established in the bed. • Hot water: hot water is distributed from burning point into various bed points through pipes that established at the base and in both sides of the bed, pipes volume and eff. Of heater and prop sloping of bed an show better heating efficiency. • Electricity: the electrical resistance which isolated by covered with lead, is distributed on soil surface and soil and along the inner side of the bed. Automatic means can be established for ventilation, irrigation < 50g mists → uniform distribution. In case of cold bed, there is no heating source. So main source of energy gaining inside it is the conserved solar radiation which related to type of cover, ventilation is important during sunny day at the morning up to afternoon not later so as to avoid sever drop in temp. during night. • *They are used for: • ear by production of seedlings especially in areas of not sever winter. • hardening of seedling that produced under heated structure.
In addition to ventilation process which prevents RH% ↑. The irrigation is done also during the morning so as to be dried out before evening (avoid risks of RH and avoid drop down of temp. as a result of water evaporation) and avoid burning spots of leaves by direct sun. 9- Low plastic tunnels: can be used for 1- seedlings production during low temp. of December and January. Can be consider as a beds or basins of 90cm × 3-4m. that seeded, irrigated then the tunnel is built over them by using galvanized wines each 1m (4-5mm as Ө ventilation done after 3weeks of seeding if temp. is low. By lifting the opposite side to prevailed wind during the day and close during night up to 10-12day before transplanting where lifting the cover completely is done. Irrigation is just at seeding time and if temp. increase another time can be done. 2- protecting plants of crops during early stages so as to have early production than open since frost risk can be avoided and reflected radiations from soil are maintained under the tunnel and protection from winds, rainfall ----- How to build the tunnel ??? after preparation.
Which can be from galvanized wires of 4-5mm Ө × 2m length or from galvanized tubes of ½ as Ө × 3m length which immersed a 1.5m space in the soil. Or could be from reinforced metallic wire of 8-10mm in Ө × 3.65m that can make an arc of 2m width as like the galvanized tubes. While the galvanized wire can make an arc 1m in width. P.E is the covering sheet of 50-80 micron and not more since it is costed and used and used for only one growing season or tow while height ranged from 45-80cm.
As the bed base increase, then thickness of the covering sheet is ↑↑ but within the range of 50-80m. and also sheet width
Tunnel Length should not exceed 30m to facilitate ventilation and improving pollination process (as a result of air shaking) for those that need pollens. • >70% of what reflected will be lost oury tunnel this % is decrease at presence of water vapor film at the inner side of plastic sheet when it is of P. Ethylene, the normal type to be used for tunnels. • Small tunnels for seedlings production and early protection while bigly ones → for protecting plant even at well developed stage. • Fiber glass, corrugated type can be used for protecting vegetables of home garden, which can be used for many times and clean easily but dimensions of tunnel should be exactly prepared with fiber glass. • Perforated plastic sheets, can be used so as to have efficient ventilation and elimination risks related to excess R H% in tunnel but this should not be highly perforated so as not to loose efficient of heating
10- Floating Covers: sheets of poly propylene that weighed 14gm/m2. as specific weight. So they are light so as to be spreaded directly over plants without inducing any damage and leaved free in order not to block plant growth allowing 80% of light tmns. • 11- Shading against strong sunlight: can be done by: • covering fruit with straw as like melons against suns cold or most of tomato plants. This method low drastically % of light to reach. • - production of vegetables under palm plants which protect vegetables from high temp., wind and direct sun shine in hot areas as Albasre. • - using plastic nets: that spreaded over frames (as those of normal tunnels). Of black or green color which transmit certain % of light according to netting intensity, the preferred is what allow to 50-60% of light transmittance so as to have 4000-5000lux of light intensity , They are treated against U.V. damage, so can remain for 3-4 years in a good state.
using of Jute sheets in nurseries to protect the tender plants during very high temp. condition or for those that considered shade loving plants. • spraying of time solution over plastic or glass covers for one or 2 times to have good shading level, stick material can be mixed with solution but washing of it later during cold condition become more difficult. (washing by spraying with 5% oxalic acid). • clay solution to be sprayed over the covers during very high temp. season to elongate growth and productive life of crop but ↓↓↓ % of transmittance light in a noticed manure, so can be applied later on when P.S. rare ↓↓ and not affect negative the yield. • - thermo blankets.
12- Plastic shelters for protection of tomato fruits from cracking as a result of heavy rainfall. This sheet is spreaded over frames of tomato crops grown in open field but vertically and also covering the sides exposed to strong wind that may also port rainfall to fruits. 13- Plastic houses: high tunnels that characterized by following points in relation to low tunnels: a- Longer period of production. b- Better vertical expansion and very high plant density (No. of plants/m2 ). c- Good production of qualified early crop that gives higher prices. d- Increase the productivity as it is possible to improve pollination and fertilization % by using Bumbles and as a real capital is employed which better factors of services and cultivation. e- Better exporting activity since the quality is more and contained for longer period. f- Easier to prepare the soil, serve plants and to overcome pests or fertilizer or water shortage problems. g- Faster cycle of the capital to have return → private sectors are highly involved in this sector -
*Glass houses: plastic houses are characterized by: • More safety against wind than pH. • Higher efficiency of solar radiation (that incident/unit time) transmittance and captured → better energy conservation. • Easier and better control of micro condition under protective G.H. structure than pH since they are provided with all facilities that. • Enable faster conditioning and minimum variation between day and might conditions. • Lower water vapor condensation → lower risk related to dropping of condensate water vapor.
*Plastic houses: Glass houses are characterized by: • Lower construction cost that = 1/10 of glass houses cost. • Arc structure of plastic house enable long period of perpendicular light/day than GH → continuous transmittance of great portion of incident solar radiation. • Changing the location of your protective structure is more easy with pH than GH which may occur every group of year for crop rotation reasons or for eliminating the risk of certain epidemic diseases since possibility of nutrient elements shortage and high diseases diffusion is very high under intensive cultivation. • Shading induced by pH frames is much lower than that induced by frames and other components of GH. • GH maintenance during its life is more applicable and costed more than pH. • pH’s are more adapted for summer and warm areas since they show lower warming condition than GH’s which are more adapted for cold regions and winter time → cooling cost is so > in GH then in pH.
Covering Materials 1-Glass: that covers that great part of glass house structure (Roof and upper party walls), non colored, pure of 3-4mm for roofs and 2.5-3mm as thickness for walls that face lower accidental weight. Glass plates dimension are of 40cm × 45-60cm, some time reach to 100cm length but the smaller the dimensions, the greater the resistance to any presser and the lower the risk to be broken and if broken the lower the cost to be changed > 90% of incident light is transmitting and low portion of that will be lost (to outside) as reradiated easy to be cleaned and of long duration up 25 year if not broken, so easy to be broken but not burned, conserve for-red radiation.
2-Plastic: either of P.E or P.V.C (poly vinyl chloride) of 180-200m for plastic houses as thickness. Treated against negative effect of U.V light so as to elongate the duration. Also can be provided with silicon atoms which keep the expansion rate at low level → better conservation of reflected light since remain straight for longer period than non treated. Double cover of plastic can be used with a space of 4-20cm (not more, not less) by pumping the air to the space. This can increase temp. inside up to 6˚c greater than out during the night of winter time. Since there is a kind of isolation. Easy to be burned, light in weight, lower cost than glass, permeable and O2, CO2 but not to water vapor, but of lower transmittance rate that is about 90% when new which decrease to 50% after one year. Allow passing of reflected for red radiation. So loss of energy from these covers is > than from glass and water drop will be condensated and after being accumulated at these rough surface (inner side) will drop down over plants → ↑ R.H% + ↑ incidence of diseases P.E is more affected by heat, light so they are changed every 2 years while P.V.C each 3 years-5 years.
3-Fiberglass: that used to cover structures that manufactured from aluminum frames with which easy to fix the fiber plates, also can be used to cover tunnels (arc length = width of fiber plate). Also can be used to cover plastic houses but should be fixed in a special way. (cross in inverted manner and straight wire over each over lapping area) plate are either corrugated or flat of (1.3m×7.3m×1cm as thick) light in w.t., allow passing of 80-90% of incident light when new, this % ↓ gradually with plate aging as a result of changes induced on plate surface which are related to environmental conditions (friction of sand particles that are carried by wind to → rough surface that enable development of decay organisms → green or black color → low transmittance percent). High in cost compared with plastic and easy to be burned. 4-Cloths: to protect the plants from insects attachment and shading plants against strong light intensity also can be used as a second door in plastic houses, GH. For having efficient control of insects filtration to cultivated plants with entrance of labors and technicians. From the kinds used: muslin, agryl.p.17 and agronet. Raished cover in west bank.
Types of plastic houses used in Jordan: • Local types: that make of water pipes that prepared manually (arcs are wounded according to model frame) from pipes of “½ -1”. Width is varied from 3.5-7m×2-2.5 height of the upper point and 1.5 is the distance between each arc and other having woody doors and plastic cover which is treated against U.V. radiation, transparent and of 80-120m and can persist to 3 seasons. • Imported types: a- Filcluir: French, of galvanized tubes that reach to mmӨ and of 64m length × 7-8.5m width ×2.75-3.2m height ×1.5m between first and arc then 3 or 2.5 or 1.5m between each other arcs. They have lefting bars as much as No. of arc for climbing of plants and rein forcing the arcs to inside they have winders for ventilation that can be opened by manawille. • b- Fornir: French, of galvanized iron 50-60mmӨ, reach to 54m length as plastic structure ×7-8-9m width ×2.65-3-3.33m as height. 1m is the distance between 1rst and 2nd are then 2-2.5m the other arcs are spacing. Having manawella to open and close the windows.
Construct ruction of protective structures • Before the establishing of P. structures, there are general conditions and others special to be taken in consideration: • The General: • 1- Capital that facilitate the application of all inputs needed for the production process (P. structures, wind breaks, seedlings production from qualified seeds, fertilizers, O.M., soil preparation and leveling, irrigation, machines, labors cost, transportation, conditioning ------etc). • 2- Presence of water sources or wells or rainfall collection as the source is closer, it will be better. • 3- Presence of roods to and from the farm to provide it with production inputs and take from the frame the product.
4- Availability of labors centers near farm area (especially at the harvest time and planting time) experienced labors are optimum. 5- Presence of professional people that can do a successful management throughout: * Employing input factors in a best manner (minimum cost → higher qualified input production and lower impact to the environment (fertilizers and pesticides). *Ready to make any design to face any sudden event so as to resolve problems related to that event in relatively short time and with minimum risks or side effects to environment. *Ready to work with his hands, to plow, to drive lorry or tractor and not feel the superiority → well trained and experienced.
*Able to use and understand the useful results of new techs that may ↑ or improve the production process as (PH meter, E.C. programming of irrigation and fertilization and computer). * Able to forecast the productivity of various crops in his region. 6- Good market facilities by instructions (cleaning, grading, packaging, labeling, cooling, distribution) and good programming for production.
The special factors: • 1- The proper location that protected from winds, building shadings or trees, connected with roads to and from the location, near to water source (good water and continuous), well drained soil (sandy to sandy loam), near to labor centers and large area that enable any future extend or development. • 2- If wind breaks are needed and natural not presented, then the construction of netted plastic breaks that allow passing 50% of the wind (filtration of wind force) which can ↓ wind speed up to 60% (40% the remain) of total wind speed at 5 × the height and up to 20% (80% the remain) of total wind speed at 20 × the height of break, so 180-240cm height are sufficient since these wind breaks rises the flow of wind up ward, that means above the top of vegetables.
3- Direction of protective structures: in calm locations, all types weather simple or multi-span should be fixed in our region at North-South direction, with which the solar radiation can reach to the plants along the day from the both longitudinal east and west sides and there is shifting of shading by frames during running of day hrs. But in windy areas, the blown winds should hit the structure in a perpendicular manner with the length of structure body (smooth hit). 4- Land leveling, sloping (especially for soil less cultivation), heating, and establishing of various facilities (election, irrigation, draining, steam system) taking in consideration that all these systems are of high cost and ↑↑ area to be covered is advised so as to ↓↓ the spent cost of all these facilities/m2 of the covered area and this within certain limits (not absolute).
5- In multi-spans → sloping of structure to certain side is important so as to collect the rainfall avoiding risks related to it’s accumulation and also can be used during water shortage if stored in prepared pools. The design, also should tolerate the possible wt’s related to snow accumulation by having additional supporting columns. Or to use single units that spaced longitudinally at 2m. 6- 60m is maximum length of the structures so as to have good ventilation and efficient movement and labors activities. 7- 2m is the minimum width (height) of the main door in both heads to allow entrance of tractors and other machines. 8- Keeping the stoages, management offices , nursery, maintenance serves at the central part.
*Construction of GH’s: that depending on special designs. The bases are prepared by engineers since not easy to be done by the farmer and so should be constructed by certain companies and what to be awarded by the farmer is the characters and purposes which can serve our plants inside the structure where certain part has been discussed and the part related to conditioning will be explained later on. *Construction of plastic houses: it varies in certain techniques from company as a producer (manufacture) to other. Each company has certain catalog that explain in detail various steps of P.H. construction where if the farmer follows can easily do the construction. And the general method includes: 1)Land leveling with dimensions ≈ equal (No. of PH. × width + m’s of space between each 2 lines) × (No. of rows × length of PH + m’s of space between each 2 rows). 2)Selecting of referring point as a partition point from which you make the angle of 90˚ by Fithagoris theory.
3)Fixing 2 pieces of │╞ as bases for both ends of the first arc, the longer side in the │╞ is immersed in soil. 4) Connecting the 4 pieces of first arc by 3 │╞ (½״ ×2״) since arc Ө is ≈ 60mm. then inserting this arc over both │╞ bases. 5) Connecting the 2 galvanized pipes of ¾״ to the 2 │╞ over the soil surface with 2 pieces of ╡╞ which supposed to fixed in soil as a bases for the next arc at the right space = to the length of the pipe. 6) Repeating step 4 to make next arc but by 3 ╡╞ (½״ ×2״) then connecting first arch with 2nd with 3 galvanized pipes of ¾״ . 7)Repeating step 6 for each arc until the last one (first arc from other side) where step 4 is repeated for it.
8)Reinforcing the first arc with the neighboring one by further pipes that ended with clips from both ends (4 for each head), these clips are fixed to pipes by screws. 9)Fixing the main bar pipes which is of greater Ө than Ө of arcs by screws, this bar is at ≈ 2m height above the soil to carry the door 10)Reinforcing the structure, also by connecting the main bar with the 2nd arc by other pips that ended with clips as mentioned in step 8. 11)Reinforcing the structure by tying the trailing wires to the main bar from each side. 12)Reinforcing the structure also by tying both outer arcs of plastic houses with No. of wires ≈ 36-34, (34= 8.5m width and 36 for 9m as width). This done by starting from upper point of the arcs (middle point) then going in both sloping sides increasing the space as we are far from middle upper point (starting with 20cm between each 2 wires as space and ending with 50-60cm down in both sides).
13)Reinforcing each arc from the inner side by connecting a pipe of (¾×״ 7-9m length = width of PH.) to hocks (collar) presented over 2nd ╬ presented over soil from each side. These pipes are also useful in carrying and trailing of the growing plants where wires that fixed longitudinally into the main bars, are passing over these pipes and No. of wire should = to No. of lines of growing crop. 14) Covering the structure as follows 15)Fixing the doors, fans, windows and roof ventilation system if presented.
The use of PH’s or GH’s • They are structures formed of iron frames having gable (جمالون) or Quonset (half cylinder) roof to avoid water or snow accumulation over the roof and so the damages related to these actions. Their volume enable entrance of labors, tractors and other machines and serving plant in an optimum way. They are of high cost but their return is profitable especially under the following conditions: • No. of structures to be utilized at the same time, effort and management (area to be covered / complete unit of services). As the area ↑ (to limit 40 structure), then the cost involved /m² covered ↓↓ under normal conditions. • Volume of covered structures (No. of m³of heated air /m² of the covered area) proportional relationship but from economic point of view it is to certain height.
3)Types of frames, woody (more shading), or Aluminum (longer duration), or galvanized iron ≈ 25 years and both Aluminum and Iron are more safety against diseases and pest, since they can’t hide while in woody yes. 4) Type of cover, wither glass, fiberglass or plastic and it’s newly degree. 5) Availability of heating, cooling, mist, irrigation system and to which level can be control automatically + presence of pool 6)Presence of most suitable cv’s, protecting condition and tolerating pollination problem + various diseases. 7)Programming of production to be at off seasons and during periods of no competition with open field production. 8) Exporting the production into outer markets (presence of facilities to export and compete out side).
*In spite of all these considerations, the protection becomes necessary in the following cases: • In cold regions and during winter: for both northern and southern sites to line 35˚ as latitude of the earth where heating is required and open field in these areas is blocked. • In Hot regions and during summer, by using conditioned GH where open field is also blocked. • While in temperate region, the protection is done by controlling the productive factors at the non favorable conditions. • *It is possible to employ the capital in a best manner through out the following points: • 40 PH (9×50m) as one unit. • Two PH as nurseries for seedlings production which can be shaded during summer by black or green plastic net.
3)Effectuating the drip system to irrigate space in between PH’s so as to be planted with low plants or covered partially with low tunnels → cost of m² to be irrigated ↓ as area to covered with drip system ↑ (within the capacity (pump + filters) of the irrigated system). 4) Distribution of crops according PH’s dimensions, volume, facilities where most valuable and tender plants supposed to be in the well prepared ones and dwarf, strawberry and lettuce in low type…….. and those that tolerate high temp. water shortage in structure of low facilities. 5) Construction of pool or tank from concrete for collecting the rainfall and storing also water from other sources during non shortage time, so as to be used at water stress or shortage time. 6)Minimizing cost of construction by use big plastic houses. 7)Availability of necessary equipments that can serve in or various activity and realize profits from various services weather in or out of the farm.
8)Presence of experienced team which ready to work at any time and any work. 9)Control the close and open of protective structures to minimize energy loss especially during winter and so ↓↓ cost of heating if system of heating is presented + using most economic, efficient and practical methods for ↓ temp. during hot summer in order to elongate the plant cycle with minimum conditioning cost. 10)Using of hybrid seeds that characterized by ↑ productivity and ↑ quality in order to achieve profits > as much as possible than the spent cost. Since these CVs are highly adapted to protect structures and for some crops are planted for more than 4-5 cycle/year under protection as like lettuce →↑↑ use of protective facilities.
Shapes of protective structures • Lean-to-building: single, beside building, sloping part towards sunshine (south and south east). • Gable uneven span: for both PH or GH, but over sides of hills so it is adapted to sloping area, can be single or multi-span but more adapted to single. • Gable even span, for both PH or GH, multi or single and it most diffused for GH over leveled land. • Gothic arc of the roof that shows pointed upper part. • Elliptical or modified Quonset that more diffused for multi-span of PH’s. • Quonset or half cylinder: just for single and more diffused for PH’s. • Methods of controlling the environmental factors in
protective structures It means to control environmental factors of atmosphere, soil factors in order to realize as much as possible the optimum conditions for plant growth → greater return/cultivated unit. The factors to be controlled are: 1)Temp: that can be modified by heating, cooling,……., which should be utilized after understanding the basic as methods of heat transport which helps in: a-Effectuating the controlling heating in efficient manner by ↑↑ % of energy gaining from solar source during the day of cold condition and by minimizing energy loss throughout reflected radiation from solid heating bodies, plants presented inside the protective structure →↑↑ cost. b- Increasing the efficiency of cooling by ↓↓ energy gaining during cooling the day of hot condition and enhancing the loss of the gained energy →↑↑ cost.
The main methods of heat transmission are: a-Radiation: light is presented as electro-magnetic wave which converted into heat as incident over bodies. So radiations that pass in plastic sheets or glass and hit bodies inside protective structures will change into heat (continuous rising in temp. of bodies as there is an incident of light. In the other hand, the heated bodies radiate energy: - loss of their heat to the cooler bodies (outer) as Far-Red. This continues as temp. inside> outside during night or day. – these facts can be useful in: a- in cold weather, it is important to maximize the solar energy gain during the day by selecting the right design, direction proper cover that allowing passing of maxi ratio + minimizing loss of Far-Red. b- In hot weather: lower light permeability to inside + higher permeability to Far-Red outside to get rid of energy presented which can induce a lot of problems. c- In temperate regions: that are of temperate weather during day and of moderate –cold during night, then the non permeable cover to Far-Red is preferred in-order to raise night temp. about 2-3˚c than out → × heating which could be in-economic in this case.
* According to their permeability to Far-Red covers can be subdivided to: • Glass + PVC of 350m → not permeable Far-Red. • Fiberglass + PVC of 75m → low permeable to Far-Red. • PE → permeable to Far-Red, but condensation of water vapor at the inner side → ×permeability since water vapor film block Far-Red filtration.
b) Conduction: transmit of energy from hot point to cold one throughout mean such as loss of energy from heated GH of ↑↑ temp to atmosphere. than outside through (in both cases) the cover. So having more than one cover (double) reduces heat loss by condition because of isolating space while in other case (gaining no need of double cover). Double cover is related to heated structures and not to these depend on Solar Radiations • Convention + infiltration: the structure body and plants presented inside are reradiating heat (after being heated by incident light) which will be carried by the means as air or water →↓ their density (heated means) → raising of air or changing water or condensate water into water vapor and going up to be replaced by colder air which in turn will gain energy and soon circulation +loss of energy as the heated means come in touch with cover or some filtrated throughout cracks, openings… • Energy reflection from sealed surfaces as the reflection of the light from sealed ironic surfaces as Far-Red.
Energy lost by conduction is expressed in British thermal units = (quantity of energy needed to raise temp. of 1pound of water a 1˚F)/this quantity to be lost through 1ft²/hr when the outer temp. is 1˚F lower than inner one. • * * Infiltrated energy is expressed in No. of air changed of protect structure/hr. energy loss by conduction is referred to a medium wend speed of 24km/hr.
